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Vitamin A for preventing acute lower respiratory tract infections in children up to seven years of age

Acute lower respiratory tract infections (LRTIs), especially pneumonia and bronchiolitis, are leading causes of mortality in children up to five years of age. The Global Burden of Disease 2000 project estimated that the annual number of acute respiratory tract infection (ARTI)-related deaths in children up to five years of age was 2.1 million (excluding deaths caused by measles, whooping cough and neonatal deaths). Others estimate worldwide child deaths from ARTIs at 1.9 million in 2000, 70% of them in Africa and Southeast Asia. Vitamin A deficiency is common in low-income countries and weakens barriers to infection.

We included 10 trials (33,179 children) where vitamin A deficiency or malnutrition was prevalent (31,379 in the community and 1800 in a hospital setting). Studies measured different aspects (for example, what constituted 'acute LRTI', the time to symptom resolution, etc.). There may have been other treatments (especially of malnourished children) which could have led to bias. Most studies showed no significant benefit of vitamin A supplements on the incidence or prevalence of symptoms of acute LRTIs. Although no included studies addressed adverse effects of vitamin A, the use of vitamin A should be carefully monitored.

We do not recommend giving vitamin A to all children to prevent acute LRTIs because a few studies unexpectedly found that vitamin A increased the chance of infections or worsened symptoms in otherwise healthy children. Some evidence shows benefit for vitamin supplements given to children with low serum retinol or with a poor nutritional status. Limitations of our review include trials conducted within very specific populations and poor methodological quality of some of the included trials.

Authors' conclusions:

This unexpected result is outside our current understanding of the use of vitamin A for preventing acute LRTIs. Accordingly, vitamin A should not be given to all children to prevent acute LRTIs. Despite its benefits in preventing diarrhoeal illnesses, vitamin A supplementation has only a limited effect in preventing acute LRTIs. Positive effects appear limited to populations with acute and chronic under nutrition. Low-dose vitamin A appears to have fewer side effects and at least equal benefit to a high dose of vitamin A.

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Background:

Vitamin A supplements are effective for preventing diarrhoea. There are theoretical reasons why they may also be effective for acute lower respiratory tract infections (LRTIs), also very common in children, especially in low-income countries.

Objectives:

To assess the effectiveness and safety of vitamin A for preventing acute LRTIs in children up to seven years of age.

Search strategy:

In this updated review we searched CENTRAL (2010, Issue 1), which contains the Cochrane Acute Respiratory Infection Group's Specialised Register, MEDLINE (1966 to February Week 4, 2010), EMBASE (1974 to March 2010) and the Chinese Databases CNKI and VIP (1976 to June 2010).

Selection criteria:

Randomised controlled trials (RCTs) that assessed the effectiveness of vitamin A in the prevention of acute LRTI in children up to seven years of age.

Ten studies including 33,179 participants were included in this review. Eight studies found no significant effect of vitamin A on the incidence of acute LRTI, or prevalence of symptoms of acute LRTI. Vitamin A caused an increased incidence of acute LRTI in one study; an increase in cough and fever; and increased symptoms of cough and rapid breathing in two other studies. Three reported no differences and no protective effect of vitamin A. Two studies reported that vitamin A significantly reduced the incidence of acute LRTI in children with poor nutritional status or weight, but increased the incidence in healthy children.

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